1. Field of the Invention
This invention relates to closed liquid coolant circulating and like systems, and particularly to such systems as they incorporate an accumulator-reservoir device of the bootstrap type.
2. Description of the Prior Art
An accumulator-reservoir device in a closed liquid circulating system exists to serve several purposes, as follows:
(a) To provide a positive pressure to the suction (intake) side of the liquid circulating pump;
(b) To accommodate changes in system liquid volume caused by changes in liquid temperature; and
(c) To provide a reserve of liquid, compensating for minor system leakage.
Known types of accumulator-reservoir devices include a piston in a cylinder mechanism defining an expansible chamber communicating with the circulating system at the suction side of the pump. In one instance this mechanism includes a spring to power the piston to maintain a pressure on the liquid in the expansion chamber. In another instance, the device is of the "bootstrap" type, that is, the piston is powered by fluid pressure from the discharge side of the pump. An example of the former construction is found in Hill, et al U.S. Pat. No. 3,559,727, issued Feb. 2, 1971. An example of the latter construction is found in Haushalter, et al U.S. Pat. No. 4,376,619, issued Mar. 15, 1983.
This invention relates to the bootstrap type device, and especially to constructions which while relatively more simple and inexpensive than prior art devices are able to meet stringent leakage and size limitations. The structure of patent No. 4,376,619 provides a chamber where high pressure liquid admitted from the discharge side of the pump acts on the piston to exert a continuing pressure on relatively low pressure liquid in the expansion chamber. The high pressure chamber is sealed from communication with ambient surroundings by a diaphragm stretched across one end of the cylinder and flexing with piston movements. The diaphragm is in large part used because it is a very effective seal against high pressure, there being some system applications for an accumulatorreservoir device having an extremely low tolerance for leakage. A diaphragm construction is, however, relatively expensive. Its flexing action can lead to excessive wear, and, usually, a cylinder extension must be provided to accommodate such flexing motion. It has been suggested that the diaphragm construction could be replaced by a sliding seal construction. However, presently known O-ring and like seals, mounted in the piston periphery or in the cylinder wall, impose an inadequate control over escape to ambient of liquid from the high pressure chamber.
The foregoing comprises a full account of pertinent prior art insofar as it is now known to the applicant and to others substantively involved in the preparation of this application.